Electrodes criticality - the impact of CRMs in the leachate electrochemical oxidation
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-01-01 |
| Journal | Manufacturing Review |
| Authors | Mattia Pierpaoli, MichaĆ Rycewicz, Aneta Ćuczkiewicz, Sylwia FudalaâKsiÄ ĆŒek, Robert Bogdanowicz |
| Institutions | GdaĆsk University of Technology, Marche Polytechnic University |
| Citations | 16 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Boron-Doped Diamond for Critical Raw Material Reduction in Electrochemical Oxidation
Section titled âTechnical Documentation & Analysis: Boron-Doped Diamond for Critical Raw Material Reduction in Electrochemical OxidationâReference: Pierpaoli et al., Electrodes criticality: the impact of CRMs in the leachate electrochemical oxidation, Manufacturing Rev. 7, 7 (2020).
Executive Summary
Section titled âExecutive SummaryâThis analysis confirms the critical role of 6CCVDâs Boron-Doped Diamond (BDD) material in developing sustainable, high-performance electrochemical oxidation (EO) systems for refractory pollutants like landfill leachate.
- BDD Superiority: Boron-Doped Diamond (BDD) electrodes are identified as the optimal compromise, offering high mineralization efficiency (COD removal) combined with the lowest Critical Raw Material (CRM) index among high-performance anodes.
- CRM Mitigation: The BDD Critical Index (Ci) (0.084-0.168) is orders of magnitude lower than traditional Noble Metal (Pt) electrodes (Ci up to 14), directly addressing EU supply risk and economic importance concerns.
- High Efficiency: BDD achieves high Chemical Oxygen Demand (COD) removal efficiencies (median ~75%) and complete Ammonium-Nitrogen (N-NH$_{4}$) removal in optimized setups.
- Fabrication Method: The research confirms that Microwave Plasma Chemical Vapor Deposition (MPCVD) is the necessary technique for producing the high-quality BDD films required for these advanced oxidation processes (AOPs).
- Scale-Up Potential: BDDâs high stability, corrosion resistance, and low CRM reliance make it uniquely suitable for the full-scale implementation of EO technology, a limitation noted for traditional Pt and MMO electrodes.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points highlight the performance and criticality comparison between BDD and conventional electrode materials analyzed in the literature review.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| BDD Critical Index (Ci) | 0.084 - 0.168 | Dimensionless | Lowest Ci among high-efficiency materials (Low CRM content) |
| Noble Metal (Pt) Critical Index (Ci) | 14 | Dimensionless | Highest Ci (High CRM content) |
| Multi-Metal Oxide (MMO) Critical Index (Ci) | 0.023 - 4.9 | Dimensionless | Highly variable, Medium/Low CRM content |
| BDD COD Removal Efficiency (Median) | ~75 | % | Achieved at low specific electrical charge (Q) |
| BDD N-NH$_{4}$ Removal Efficiency (Range) | 25 - 100 | % | Dependent on boron doping ratio (sp3/sp2) |
| BDD Key Advantages | High stability, wide potential window, chemical inertness | N/A | Superior durability and oxidation potential |
| Substrates Reported for BDD Growth | Si, Nb, Ti, Glassy Carbon | N/A | Required for DSA fabrication |
Key Methodologies
Section titled âKey MethodologiesâThe study utilized a comprehensive literature review and quantitative analysis to compare electrode performance and material criticality.
- Electrode Classification: Electrodes were categorized based on material type: Noble Metal (Pt), Lead Dioxide (PbO$_{2}$), Single-Metal Oxide (SMO), Multi-Metal Oxide (MMO), Amorphous Carbon (a-C), and Boron-Doped Diamond (BDD).
- BDD Fabrication Method: BDD electrodes were produced using Microwave Plasma Chemical Vapor Deposition (MPCVD), allowing for precise control over the boron doping level.
- Criticality Index (Ci) Calculation: The Ci was computed using the Euclidean distance between the weighted Supply Risk (SR) and Economic Importance (EI) indexes, normalized by electrode area, element fraction ratio, and atomic weight (Equation 2).
- Data Collection: 112 observations were collected from 25 publications focusing on EO of landfill leachate. Experimental data included initial COD/N-NH$_{4}$ concentrations, current density, and test duration.
- Performance Metrics: Efficiency was evaluated based on Chemical Oxygen Demand (COD) removal and Ammonium-Nitrogen (N-NH$_{4}$) removal percentages.
- Correlation Analysis: Critical Index values were plotted against COD and N-NH$_{4}$ removal efficiencies to determine the optimal balance between sustainability and performance (Figures 6 and 7).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the advanced BDD materials required to replicate and scale the high-efficiency, low-criticality electrochemical oxidation systems detailed in this research. Our expertise in MPCVD diamond growth ensures materials meet the stringent requirements for AOP applications.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend this research, engineers require high-quality, customized BDD material:
- Heavy Boron Doped PCD (Polycrystalline Diamond): Essential for high mineralization efficiency and low CRM content. 6CCVD specializes in tuning the boron concentration to optimize the sp3/sp2 ratio, which the paper notes is critical for maximizing N-NH$_{4}$ removal efficiency.
- Custom Substrates: While Si is commonly reported, 6CCVD offers BDD growth on application-specific substrates, including Ti and Nb, which are preferred for robust Dimensionally Stable Anodes (DSAs) due to their electrical conductivity and thermal resistance.
Customization Potential
Section titled âCustomization PotentialâThe transition from laboratory studies to full-scale implementation requires materials with specific dimensions and integration features. 6CCVD provides comprehensive customization services:
| Requirement from Research | 6CCVD Capability | Specification Range |
|---|---|---|
| Large Area Electrodes (For scale-up) | Custom PCD Plates/Wafers | Up to 125mm diameter |
| Active Layer Thickness | Precision BDD Layer Growth | 0.1 ”m - 500 ”m |
| Electrode Integration | Custom Metalization Services | Au, Pt, Pd, Ti, W, Cu contacts available |
| Surface Finish | Polishing for Enhanced Contact | Ra < 5 nm (PCD) |
| Custom Doping | Tunable Boron Concentration | Optimized for specific EO/AOP applications |
Engineering Support
Section titled âEngineering SupportâThe paper highlights that BDD performance is highly dependent on the boron doping level and the resulting sp3/sp2 ratio. 6CCVDâs in-house PhD team specializes in material science and can assist researchers and engineers with:
- Material Selection: Guidance on selecting the optimal BDD grade (PCD vs. SCD) and substrate (Ti, Si, Nb) for specific leachate compositions and reactor designs.
- Doping Optimization: Consultation on tuning boron concentration to maximize selectivity and removal rates for target pollutants (e.g., optimizing BDD for N-NH$_{4}$ conversion to nitrate).
- Integration Design: Support for metalization schemes (e.g., Ti/Pt/Au) and mechanical integration of diamond plates into industrial electrochemical cells.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Landfill leachate possesses high concentrations of ammonia, micropollutants, and heavy metals, and are characterised for low biodegradability. For this reason, conventional treatment technologies may result ineffective for complete pollutant removal. Electrochemical oxidation allows most of the of recalcitrant pollutants to be oxidised effectively within an easy operational and acceptable retention time, without the need to provide additional chemicals, and without producing waste materials. The mineralisation efficiency and electrode durability depend on the nature of the electrode material. The conventionally adopted anodes can contain critical raw materials (CRMs), and are subject to extreme corrosion conditions. CRM-free electrodes, such as carbon and graphite-based, exhibit a lower efficiency, and are subject to faster deactivation, or, as for lead-dioxide-based electrodes, can constitute a hazard due to the release into the effluent of the coating corrosion products. In this study, the relationship between electrode type, CRM content, and the removal efficiencies of organic compounds and ammonium-nitrogen (N-NH 4 ) was investigated. Material criticality was estimated by the supply risk with economic importance indexes reported in the 2017 EU CRM List. The COD and N-NH 4 removal efficiencies were obtained from a literature analysis of 25 publications. The results show that, while single and multi-oxide-coated electrodes may contain low amounts of CRM, but with limited efficiency, boron-doped diamonds (BDD) may constitute the best compromise in terms of a reduced content of CRM and a high mineralisation efficiency.